Abstract: It intends to prevent the reduction in quantity with time of an oxyl compound in vinyl compounds. The quantity reduction of the N-oxyl compound is suppressed by causing an N-oxyl compound, N-hydroxy-2,2,6,6-tetramethylpiperidine compound and a 2,2,6,6-tetramethylpiperidine compound to co-exist in vinyl compounds.

Abstract: The present invention provides a production process for a hydroxyalkyl (meth)acrylate which process enables to maintain the oxygen concentration of a gas phase portion of a reactor within a specific low concentration range in any stage of before adding raw materials, during the reaction, and after the reaction. The production process comprises the step of carrying out a reaction between (meth)acrylic acid and an alkylene oxide in the presence of a catalyst in order to produce the hydroxyalkyl (meth)acrylate, wherein an inert gas and/or a mixed gas of oxygen and an inert gas with a beforehand adjusted oxygen concentration of 0.1 to 14 vol % is used to maintain the oxygen concentration of a gas phase portion of a reactor in the range of 0.1 to 14 vol % (1) before adding the alkylene oxide or (2) during the above reaction or (3) between the completion of the above reaction and the charge for the next reaction.

Abstract: A method of producing highly purified acrylic acid in a high yield is provided. A method of producing acrylic acid including the steps of an oxidation step, an absorption step, a distillation step, a crystallization step, and a dimer decomposition step.

Abstract: This invention relates to a storage tank for a viscous oil containing easily polymerizable compounds. A storage tank of the present invention for strong viscous oil containing easily polymerizable compounds, comprising a bottom plate 12, a side wall 13, a draw-off pipe 3 and a inlet pipe 2. The bottom plate 12 slopes downward toward the draw-off pipe 3 and an angle of downward inclination of the bottom plate 12 is gradient at least 1/200. It becomes possible by the present inventive storage tank to effectively prevent the polymerization of the easily polymerizable compounds contained in the waste oil within the storage tank and the clogging of a pipe is suppressed considerably.

Abstract: A method for producing (meth) acrylic acid of high purity by repressing formation of a polymer possibly generated during the course of production is disclosed. The production is accomplished by returning the waste liquid generated at the step of the addition of aldehyde treating agents (d) to the step of the absorption (b) and/or the step of separation (c).

Abstract: The present invention provides a heat-exchanging method for an easily polymerizable compound which method effectively prevents polymerization in a heat exchanger to enable a long-term stable heat exchange when an easily polymerizable liquid compound (for example, acrylate ester) or an easily polymerizable compound-containing liquid (for example, aqueous acrylic acid solution) is heat-exchanged. A vertical spiral type heat exchanger with a fluid path space of not less than 6 mm is used as a heat exchanger to carry out the heat exchange under conditions where the average liquid flow rate is not less than 0.2 m/sec and where the liquid residence time is not more than 100 seconds.

Abstract: A method for washing a spent solid catalyst is disclosed which is characterized by washing the solid catalyst used for the reaction of generating an esterified compound in a device packed with the solid catalyst, distilling the cleaning fluid in a distilling part, and circulating the fraction obtained by the distillation to an esterification reactor. According to this invention, the existing apparatus used during the process for the production of an esterified compound can be adopted without any modification, the water by-produced in the reaction for production an esterified compound and an alcohol as the raw material for esterification can be used as the cleaning fluid, and these effective components can be recovered from the cleaning fluid. Thus, the stimulation from the offensive odor and the volatile component which has heretofore posed a problem during the removal of the solid catalyst is eliminated and the safety in terms of heath and in terms of operation is secured.

Abstract: The present invention provides an apparatus for producing (meth)acrylic acid and a process for producing (meth)acrylic acid with this apparatus wherein the apparatus enables to produce (meth)acrylic acid stably for a long period of time by effectively inhibiting the polymerization of (meth)acrylic acid in its production process (for example, in a reboiler). At least a part of the apparatus is made of a nickel-chromium-iron alloy with a molybdenum content of 3 to 20 mass %, but not including 3 mass %, or with a molybdenum content of 1 to 4 mass % and a copper content of 0.5 to 7 mass %.

Abstract: The present invention provides an industrially easy and economical method for purification of acrylic acid which enables to efficiently eliminate impurities from a crude acrylic acid containing aldehydes as the impurities while the formation of acrylic acid polymer is inhibited.

Abstract: It intends to prevent the reduction in quantity with time of an N-oxyl compound in vinyl compounds. The quantity reduction of the N-oxyl compound is suppressed by causing an N-oxyl compound, N-hydroxy-2,2,6,6-tetramethylpiperidine compound and a 2,2,6,6-tetramethylpiperidine compound to co-exist in vinyl compounds.

Abstract: For use in a process for the production of (meth)acrylic acid comprising at least a step for the reaction of (meth)acrylic acid by catalytic gas phase oxidation and a step for the absorption thereof, a method for preventing an effluent gas pipe from blocking is disclosed, which method is characterized by causing part or the whole of the gas discharged from the step for absorption, while being circulated via the effluent gas pipe to the step for the reaction or being discarded, to be subjected to temperature elevation and application of pressure and/or mist separation. Particularly by setting the temperature of the waste gas from the absorption column at a level in the range of 30-70° C.

Abstract: An improved method which enables stable and effective recovery of acrylic acid over a prolonged period is provided, said method comprising contacting an acrylic acid-containing gas obtained upon gas-phase catalytic oxidation of propylene and/or acrolein, with water, whereby collecting the acrylic acid in form of an aqueous solution, introducing said aqueous solution into an azeotropic separation column and distilling it in the presence of an azeotropic solvent to isolate and recover the acrylic acid, in which polymerization of the acrylic acid in the azeotropic separation column is prevented. Said method is characterized by using as the azeotropic solvent either a mixed solvent composed of solvent A (eg., ethyl acrylate, methyl methacrylate, etc.) and solvent B (eg., toluene, heptane, etc.) (first embodiment) or the solvent A alone (second embodiment).

Abstract: The present invention provides an improved process for production of acrylic acid by subjecting propylene and/or acrolein to catalytic gas-phase oxidation with a molecular oxygen-containing gas. In the process, the mixed gas obtained by the catalytic gas-phase oxidation is contacted with an aqueous collecting agent containing acrylic acid, acetic acid and a poorly-soluble-in-water solvent, to form an aqueous acrylic acid solution; and the aqueous acrylic acid solution is subjected to azeotropic distillation in the presence of a poorly-soluble-in-water solvent to remove by-products and obtain high-purity acrylic acid.